1. Field
This application relates generally to wireless communication and more specifically, but not exclusively, to controlling access point transmit power.
2. Introduction
A wireless communication network may be deployed over a geographical area to provide various types of services (e.g., voice, data, multimedia services, etc.) to users within that geographical area. In a typical implementation, macro access points (e.g., each of which provides service via one or more cells) are distributed throughout a macro network to provide wireless connectivity for access terminals (e.g., cell phones) that are operating within the geographical area served by the macro network.
As the demand for high-rate and multimedia data services rapidly grows, there lies a challenge to implement efficient and robust communication systems with enhanced performance. To supplement conventional network access points (e.g., to provide extended network coverage), small-coverage access points (e.g., low power access points) may be deployed to provide more robust indoor wireless coverage or other coverage to access terminals inside homes, enterprise locations (e.g., offices), or other locations. Such small-coverage access points may be referred to as, for example, femto cells, femto access points, home NodeBs, home eNodeBs, or access point base stations. Typically, such small-coverage access points are connected to the Internet and the mobile operator's network via a DSL router or a cable modem. For convenience, small-coverage access points may be referred to as femto cells or femto access points in the discussion that follows.
When a femto cell is deployed on a carrier frequency that is different from the carrier frequencies used by neighboring macro cells, the femto cell may radiate beacons on the macro cell carrier frequencies. In this way, the femto cell may attract an access terminal that is in the vicinity of the femto cell to the femto cell coverage (i.e., cause the access terminal to move off of the macro cell coverage). Thus, through the use of this beacon scheme, a user coming home (e.g., approaching a home femto cell) from outside the coverage of the femto cell will be able to readily discover the femto cell and obtain service from the femto cell. Though such beacons are useful in terms of femto cell discovery, they may create interference on the macro network since the beacons are transmitted on the same carrier frequency that is used by neighboring macro cells. This interference may affect the voice call quality of active macro cell users (i.e., users actively receiving service from one or more macro cells on a macro cell frequency) and may also lead to call drops if the macro cell user happens to be very close to the femto cell. Similar macro network interference issues may arise in a co-channel deployment due to femto cell forward link transmissions. Therefore, there is a need to protect active macro cell users from interference from femto cells while still providing adequate coverage at a femto cell.